The most common method for recovering a copper sulfide concentrate from an ore is by froth flotation. The ore is wet ground to form a mineral pulp, which is usually conditioned with a collector compound that adsorbs to the surface of copper sulfide minerals and makes the surface of copper sulfide minerals more hydrophobic. A gas is then passed through the mineral pulp to form gas bubbles, hydrophobic particles of the mineral pulp attach predominantly to the gas/liquid phase boundary of the bubbles and are carried with the gas bubbles to the froth that forms on top of the mineral pulp. The froth is removed from the liquid surface to recover a copper sulfide concentrate.
Wet grinding of the mineral pulp is usually carried out with steel grinding media, most commonly steel balls in a ball mill. It is known that use of high chromium cast iron alloy grinding media can improve the recovery of copper sulfides during flotation as compared to the use of carbon steel grinding media. It is believed that corrosion of carbon steel and adsorption of iron species, formed by such corrosion, onto the surface of copper sulfides depresses flotation of copper sulfides and that high chromium cast iron alloy grinding media improve recovery of copper sulfides during flotation due to the better corrosion resistance of such alloys.
Most copper sulfide ores contain iron sulfides in addition to copper sulfides and one aims at achieving selective flotation of copper sulfides, with iron sulfides remaining in the flotation tailings.
U.S. Pat. No. 5,110,455 discloses a method for separating copper sulfide from rimmed iron sulfide which uses conditioning of the mineral pulp with an oxidant that is preferably hydrogen peroxide. The document teaches to add an oxidant in an amount that raises the redox potential of the mineral pulp by 20 to 500 mV.
A Uribe-Salas et al., Int. J. Miner. Process. 59 (2000) 69-83 describe an improvement in the selectivity for the flotation of chalcopyrite from an ore of pyrite matrix by raising the redox potential of the mineral pulp by 0.1 V through an addition of hydrogen peroxide before flotation. The amount of hydrogen peroxide added is adjusted to provide a constant redox potential.